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feat(chain): BIP84 derivation + BIP143 SegWit signing for BTC sweeps

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BtcDriver::sendNative only supported legacy P2PKH (BIP44) inputs:
it derived a P2PKH address from the mnemonic, fetched UTXOs there,
and signed with the legacy pre-segwit sighash. Sweeping a bc1q
(Native SegWit / BIP84) wallet therefore failed: UTXOs were fetched
for the wrong (P2PKH) address, and even if found, the legacy sighash
would produce an invalid signature.

- ChainDriver::sendNative gains an optional ?string $from param so the
  driver knows which address it is sweeping (TransferService passes it).
- BtcDriver::fromType classifies the from address: P2PKH (1...) and
  P2WPKH (bc1q v0+20) are spendable; P2SH/P2WSH/P2TR are rejected
  with explicit errors (Taproot-from needs Schnorr/BIP341, deferred).
- sendNative picks BIP44 (m/44'/0'/0'/0/i) for P2PKH and BIP84
  (m/84'/0'/0'/0/i) for P2WPKH, derives the key, and asserts the
  derived address equals the requested from address.
- New buildAndSignSegwit implements BIP143 SIGHASH_ALL for P2WPKH
  (hashPrevouts/hashSequence/hashOutputs, per-input scriptCode
  1976a914<20>88ac + amount), emits the segwit serialization
  (marker 0x00 / flag 0x01, empty scriptSig, witness <sig> <pubkey>).
- estimateFee gains a $segwit flag using P2WPKH vsize
  (11 + 68*in + 43*out) so fee math is correct for segwit sweeps.
- Legacy P2PKH path (buildAndSign) is unchanged; from=null keeps the
  original behaviour.

Verified locally: BIP84 index 0 of the standard test mnemonic derives
the canonical bc1qcr8te4kr609gcawutmrza0j4xv80jy8z306fyu; BIP143 sighash
cross-checks against an independent implementation; the produced
witness signature verifies (EC) over that sighash; tx structure parses
(marker/flag/empty scriptSig/2-item witness) and txid is well-formed.

Co-authored-by: Cursor <cursoragent@cursor.com>
This commit is contained in:
root
2026-10-02 19:41:27 +00:00
parent 30357c108f
commit 529ae4aa38
6 changed files with 177 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files
app/Services/Chain/BtcDriver.php
+170 -8
View File
@@ -33,14 +33,31 @@ class BtcDriver implements ChainDriver
return BtcAddress::p2wpkhFromCompressedPublicKey($compressed);
}
public function sendNative(string $mnemonic, int $index, string $to, string $amount): string
public function sendNative(string $mnemonic, int $index, string $to, string $amount, ?string $from = null): string
{
if (! $this->isValidAddress($to)) {
throw new RuntimeException('Invalid BTC address');
}
$derived = Bip44::derive($mnemonic, $this->path($index));
$from = BtcAddress::fromPrivateKey($derived['private_key']);
// Resolve the from-address type. Default to legacy P2PKH (BIP44) when no
// from address is supplied, preserving the original behaviour.
$fromType = $from === null ? 'p2pkh' : $this->fromType($from);
$segwit = $fromType === 'p2wpkh';
$derived = Bip44::derive(
$mnemonic,
$segwit ? $this->pathBip84($index) : $this->path($index),
);
$compressed = BtcAddress::compressedPublicKey($derived['private_key']);
$derivedFrom = $segwit
? BtcAddress::p2wpkhFromCompressedPublicKey($compressed)
: BtcAddress::p2pkhFromCompressedPublicKey($compressed);
if ($from !== null && $from !== $derivedFrom) {
throw new RuntimeException('BTC from address does not match derived key');
}
$from = $derivedFrom;
$amountSats = $this->toSats($amount);
$utxos = $this->fetchUtxos($from);
@@ -57,17 +74,17 @@ class BtcDriver implements ChainDriver
foreach ($utxos as $utxo) {
$selected[] = $utxo;
$totalIn = bcadd($totalIn, (string) $utxo['value'], 0);
$fee = $this->estimateFee(count($selected), 2, $feeRate);
$fee = $this->estimateFee(count($selected), 2, $feeRate, $segwit);
if (bccomp($totalIn, bcadd($target, (string) $fee, 0), 0) >= 0) {
break;
}
}
$fee = $this->estimateFee(count($selected), 2, $feeRate);
$fee = $this->estimateFee(count($selected), 2, $feeRate, $segwit);
$needed = bcadd($target, (string) $fee, 0);
if (bccomp($totalIn, $needed, 0) < 0) {
// Try with single output (no change) — dust change becomes fee.
$fee1 = $this->estimateFee(count($selected), 1, $feeRate);
$fee1 = $this->estimateFee(count($selected), 1, $feeRate, $segwit);
$needed1 = bcadd($target, (string) $fee1, 0);
if (bccomp($totalIn, $needed1, 0) < 0) {
throw new RuntimeException('Insufficient BTC balance for amount+fee');
@@ -90,7 +107,13 @@ class BtcDriver implements ChainDriver
$outputs[] = ['script' => $changeScript, 'value' => $change];
}
if ($segwit) {
$keyhash = bin2hex(hash('ripemd160', hash('sha256', hex2bin($compressed), true), true));
$raw = $this->buildAndSignSegwit($selected, $outputs, $derived['private_key'], $keyhash);
} else {
$raw = $this->buildAndSign($selected, $outputs, $derived['private_key']);
}
$txid = $this->broadcast($raw);
if ($txid === '') {
throw new RuntimeException('BTC broadcast failed');
@@ -99,6 +122,40 @@ class BtcDriver implements ChainDriver
return $txid;
}
/**
* Classify a BTC from-address for spending. Only single-key P2PKH and
* P2WPKH are spendable here; P2SH/P2WSH/P2TR are rejected explicitly.
*
* @return string 'p2pkh' | 'p2wpkh'
*/
private function fromType(string $from): string
{
$from = trim($from);
if (preg_match('/^bc1/i', $from)) {
$d = BtcAddress::decodeBech32($from);
if ($d['version'] === 0 && strlen($d['program']) === 20) {
return 'p2wpkh';
}
if ($d['version'] === 1 && strlen($d['program']) === 32) {
throw new RuntimeException('Spending from Taproot (P2TR) is not supported yet');
}
if ($d['version'] === 0 && strlen($d['program']) === 32) {
throw new RuntimeException('Spending from P2WSH is not supported');
}
throw new RuntimeException('Unsupported SegWit from address');
}
$hex = TronAddress::base58CheckToHex($from);
$ver = substr($hex, 0, 2);
if ($ver === '00') {
return 'p2pkh';
}
if ($ver === '05') {
throw new RuntimeException('Spending from P2SH is not supported');
}
throw new RuntimeException('Unsupported BTC from address');
}
public function sendToken(string $mnemonic, int $index, string $to, string $amount, string $contract): string
{
throw new RuntimeException('BTC does not support token transfers');
@@ -286,10 +343,13 @@ class BtcDriver implements ChainDriver
return 10;
}
private function estimateFee(int $inputs, int $outputs, int $satPerVbyte): int
private function estimateFee(int $inputs, int $outputs, int $satPerVbyte, bool $segwit = false): int
{
// Legacy P2PKH approx: 10 + 148*in + 34*out
$vsize = 10 + (148 * $inputs) + (34 * $outputs);
// P2WPKH approx (vsize): 11 + 68*in + 43*out (43 covers P2TR outputs; overestimates slightly, safe)
$vsize = $segwit
? 11 + (68 * $inputs) + (43 * $outputs)
: 10 + (148 * $inputs) + (34 * $outputs);
return max(1, $vsize * max(1, $satPerVbyte));
}
@@ -352,6 +412,108 @@ class BtcDriver implements ChainDriver
return bin2hex($version.$vinCount.$signedVins.$voutCount.$voutPayload.$locktime);
}
/**
* Build and sign a SegWit transaction spending P2WPKH inputs (BIP143).
*
* @param list<array{txid: string, vout: int, value: int, scriptpubkey: string}> $inputs
* @param list<array{script: string, value: string}> $outputs
* @param string $privateKeyHex hex private key for the P2WPKH keypair
* @param string $keyhashHex 20-byte hash160 of the compressed pubkey (hex)
*/
private function buildAndSignSegwit(array $inputs, array $outputs, string $privateKeyHex, string $keyhashHex): string
{
$version = $this->u32le(1);
$locktime = $this->u32le(0);
$marker = "\x00";
$flag = "\x01";
$voutCount = $this->varInt(count($outputs));
$voutPayload = '';
foreach ($outputs as $out) {
$voutPayload .= $this->u64le($out['value']);
$script = hex2bin($out['script']);
if ($script === false) {
throw new RuntimeException('Invalid output script');
}
$voutPayload .= $this->varInt(strlen($script)).$script;
}
$pub = hex2bin(BtcAddress::compressedPublicKey($privateKeyHex));
if ($pub === false) {
throw new RuntimeException('Invalid public key');
}
$witnesses = '';
$vinPayload = '';
foreach ($inputs as $i => $in) {
$hash = $this->segwitSighashAll($inputs, $outputs, $i, $keyhashHex);
$der = $this->signDer($privateKeyHex, $hash)."\x01"; // SIGHASH_ALL
$witness = $this->varInt(2) // 2 stack items: <sig> <pubkey>
.$this->pushData($der)
.$this->pushData($pub);
$witnesses .= $witness;
$vinPayload .= $this->outpoint($in['txid'], $in['vout']);
$vinPayload .= $this->varInt(0); // empty scriptSig for native SegWit
$vinPayload .= $this->u32le(0xffffffff);
}
$vinCount = $this->varInt(count($inputs));
return bin2hex($version.$marker.$flag.$vinCount.$vinPayload.$voutCount.$voutPayload.$witnesses.$locktime);
}
/**
* BIP143 SIGHASH_ALL sighash for a P2WPKH input (32-byte raw binary).
*
* @param list<array{txid: string, vout: int, value: int, scriptpubkey: string}> $inputs
* @param list<array{script: string, value: string}> $outputs
*/
private function segwitSighashAll(array $inputs, array $outputs, int $inputIndex, string $keyhashHex): string
{
$version = $this->u32le(1);
$locktime = $this->u32le(0);
$prevouts = '';
$sequences = '';
foreach ($inputs as $in) {
$prevouts .= $this->outpoint($in['txid'], $in['vout']);
$sequences .= $this->u32le(0xffffffff);
}
$hashPrevouts = hash('sha256', hash('sha256', $prevouts, true), true);
$hashSequence = hash('sha256', hash('sha256', $sequences, true), true);
$hashOutputsData = '';
foreach ($outputs as $out) {
$script = hex2bin($out['script']);
if ($script === false) {
throw new RuntimeException('Invalid output script');
}
$hashOutputsData .= $this->u64le($out['value']).$this->varInt(strlen($script)).$script;
}
$hashOutputs = hash('sha256', hash('sha256', $hashOutputsData, true), true);
$scriptCode = hex2bin('1976a914'.$keyhashHex.'88ac');
if ($scriptCode === false) {
throw new RuntimeException('Invalid P2WPKH scriptCode');
}
$in = $inputs[$inputIndex];
$preimage = $version
.$hashPrevouts
.$hashSequence
.$this->outpoint($in['txid'], $in['vout'])
.$this->varInt(strlen($scriptCode)).$scriptCode
.$this->u64le((string) $in['value'])
.$this->u32le(0xffffffff)
.$hashOutputs
.$locktime
.$this->u32le(1); // SIGHASH_ALL
return hash('sha256', hash('sha256', $preimage, true), true);
}
private function signDer(string $privateKey, string $hash32): string
{
$ec = new EC('secp256k1');
app/Services/Chain/ChainDriver.php
+1 -1
View File
@@ -11,7 +11,7 @@ interface ChainDriver
/**
* @return string txid
*/
public function sendNative(string $mnemonic, int $index, string $to, string $amount): string;
public function sendNative(string $mnemonic, int $index, string $to, string $amount, ?string $from = null): string;
/**
* @return string txid
app/Services/Chain/EthDriver.php
+1 -1
View File
@@ -20,7 +20,7 @@ class EthDriver implements ChainDriver
return EthAddress::fromUncompressedPublicKey($derived['public_key_uncompressed']);
}
public function sendNative(string $mnemonic, int $index, string $to, string $amount): string
public function sendNative(string $mnemonic, int $index, string $to, string $amount, ?string $from = null): string
{
if (! $this->isValidAddress($to)) {
throw new RuntimeException('Invalid ETH address');
app/Services/Chain/SolDriver.php
+1 -1
View File
@@ -24,7 +24,7 @@ class SolDriver implements ChainDriver
return SolAddress::fromMnemonic($mnemonic, $index);
}
public function sendNative(string $mnemonic, int $index, string $to, string $amount): string
public function sendNative(string $mnemonic, int $index, string $to, string $amount, ?string $from = null): string
{
throw new RuntimeException('SOL native transfer not supported');
}
app/Services/Chain/TronDriver.php
+1 -1
View File
@@ -20,7 +20,7 @@ class TronDriver implements ChainDriver
return TronAddress::fromUncompressedPublicKey($derived['public_key_uncompressed']);
}
public function sendNative(string $mnemonic, int $index, string $to, string $amount): string
public function sendNative(string $mnemonic, int $index, string $to, string $amount, ?string $from = null): string
{
if (! $this->isValidAddress($to)) {
throw new RuntimeException('Invalid Tron address');
app/Services/TransferService.php
+2 -2
View File
@@ -105,7 +105,7 @@ class TransferService
}
$txid = match ($asset) {
'TRX', 'ETH', 'BTC' => $driver->sendNative($mnemonic, $index, $to, $amount),
'TRX', 'ETH', 'BTC' => $driver->sendNative($mnemonic, $index, $to, $amount, $fromAddress),
'USDT' => $driver->sendToken(
$mnemonic,
$index,
@@ -113,7 +113,7 @@ class TransferService
$amount,
$this->usdtContract($chain),
),
'BNB' => $driver->sendNative($mnemonic, $index, $to, $amount),
'BNB' => $driver->sendNative($mnemonic, $index, $to, $amount, $fromAddress),
default => throw new RuntimeException("Unsupported asset: {$asset}"),
};